I have created the schematic below, but I have some doubts if this will work. I have concerns in that the AD7740 needs a power in, so where does the battery get grounded? Also, Is there another temperature sensor that can be used to simplify this circuit?

I do apologize if I am asking redundant questions or if I am way off. I have been removed from electronics for the past 15 yrs or so and I am trying to get back in and reading everythnig that I can.